Geopolymer is a cementitious material that has the potential to be an alternative to the ordinary portland cement (OPC). Unlike the mechanism of hydraulic and/or pozzolanic reactions for the formation of OPC, geopolymers can be prepared when source materials including an alumina silicate material (such as fly ash, slag, etc.) and an alkaline reagent (such as sodium or potassium hydroxide) react and form an inorganic polymer-like structure, which can serve as a binder. As described by Davidovits et al. in U.S. Pat. No. 8,202,362 B2, the geopolymer network includes SiO4 and AlO4 tetrahedrons alternatively bound by oxygen atoms. Cations present in structural cavities balance negative charges.
There is a rising interest in geopolymers due, at least in part, to increasing emphasis on sustainability. The production of one metric ton of hydraulic cement generates approximately 1 metric ton of carbon dioxide (CO2). The production of geopolymeric cement releases 5 to 10 times less CO2. See Davidovits, World Resource Review, 6(2), pp. 263-278 (1994). Geopolymers also have many other advantages over OPC, such as high strength, high temperature resistance, and acid resistance.
However, the production of geopolymers based on fly ash at ambient temperatures has proven to be a challenge. Previous geopolymer studies have indicated a possible temperature threshold and that strength development under the temperature threshold is too slow for civil engineering applications. See Hardiito et al., Australian Journal of Structural Engineering, 61(1), 77 (2005). Geopolymers are typically cured at temperatures ranging between 50 and 80° C. using added heat from an external source. Because the typical curing temperature is higher than ambient temperature, the utilization of geopolymer as a construction material is impeded. See Petermann et al., Alkali-Activated Geopolymers: A Literature Review, DTIC Document, 2010.
Accordingly, there is a need for additional geopolymer compositions and methods of production, particularly for geopolymer compositions that can be cured and/or that develop good strength at ambient temperatures. There is also an ongoing need for green building materials that can produce less waste and/or that can utilize waste products from other industries.